U.S. patent number 6,958,730 [Application Number 10/100,122] was granted by the patent office on 2005-10-25 for antenna device and radio communication equipment including the same.
This patent grant is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to Takashi Ishihara, Shoji Nagumo, Kengo Onaka, Jin Sato.
United States Patent |
6,958,730 |
Nagumo , et al. |
October 25, 2005 |
Antenna device and radio communication equipment including the
same
Abstract
A feed radiation electrode including two branched radiation
electrodes is provided on the surface of a substrate. Non-feed
radiation electrodes are provided on both sides of the feed
radiation electrode and near the branched radiation electrodes. The
branched radiation electrode and the non-feed radiation electrode
are double-resonated in the same frequency band. The branched
radiation electrode and the non-feed radiation electrode are
double-resonated in the same frequency band which is higher than
that of the branched radiation electrode and the non-feed radiation
electrode.
Inventors: |
Nagumo; Shoji (Kawasaki,
JP), Onaka; Kengo (Yokohama, JP), Ishihara;
Takashi (Machida, JP), Sato; Jin (Sagamihara,
JP) |
Assignee: |
Murata Manufacturing Co., Ltd.
(Kyoto, JP)
|
Family
ID: |
18982796 |
Appl.
No.: |
10/100,122 |
Filed: |
March 19, 2002 |
Foreign Application Priority Data
|
|
|
|
|
May 2, 2001 [JP] |
|
|
2001-135310 |
|
Current U.S.
Class: |
343/702; 343/829;
343/846 |
Current CPC
Class: |
H01Q
1/2283 (20130101); H01Q 9/0421 (20130101); H01Q
5/378 (20150115); H01Q 5/371 (20150115); H01Q
11/20 (20130101) |
Current International
Class: |
H01Q
11/00 (20060101); H01Q 5/00 (20060101); H01Q
1/22 (20060101); H01Q 11/20 (20060101); H01Q
001/24 () |
Field of
Search: |
;343/700MS,702,713,795,829,830,846,848,833,834 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 655 797 |
|
May 1995 |
|
EP |
|
0 790 663 |
|
Aug 1997 |
|
EP |
|
0 831 547 |
|
Mar 1998 |
|
EP |
|
GB 2 355 114 |
|
Apr 2001 |
|
EP |
|
1 143 558 |
|
Oct 2001 |
|
EP |
|
06-069715 |
|
Mar 1994 |
|
JP |
|
06-181997 |
|
Jul 1994 |
|
JP |
|
06-291530 |
|
Oct 1994 |
|
JP |
|
08-250917 |
|
Sep 1996 |
|
JP |
|
10-093332 |
|
Apr 1998 |
|
JP |
|
10-200327 |
|
Jul 1998 |
|
JP |
|
10-247807 |
|
Sep 1998 |
|
JP |
|
11-004117 |
|
Jan 1999 |
|
JP |
|
11-127014 |
|
May 1999 |
|
JP |
|
2000-134027 |
|
May 2000 |
|
JP |
|
2000-151258 |
|
May 2000 |
|
JP |
|
2001-007639 |
|
Jan 2001 |
|
JP |
|
2001-68917 |
|
Mar 2001 |
|
JP |
|
WO 01/18909 |
|
Mar 2001 |
|
WO |
|
WO 01/24316 |
|
Apr 2001 |
|
WO |
|
WO 01/33665 |
|
May 2001 |
|
WO |
|
Primary Examiner: Wimer; Michael C.
Attorney, Agent or Firm: Keating & Bennett, LLP
Claims
What is claimed is:
1. An antenna device comprising: a substrate made of one of a
dielectric material and a magnetic material; a feed element
disposed on the substrate and including a feeding terminal and a
feed radiation electrode electrically coupled to the feeding
terminal, the feed radiation electrode including a plurality of
branched radiation electrodes, each of the plurality of branched
radiation electrodes having one common end and extended ends
defining open ends; and a plurality of non-feed elements disposed
on the substrate, each of the plurality of non-feed elements
including a ground terminal and a non-feed radiation electrode
electrically coupled to the ground terminal, the non-feed radiation
electrode extending from the ground terminal and including an
extended end defining an open end; wherein each of the plurality of
non-feed radiation electrodes is disposed along and in the vicinity
of a respective one of the plurality of branched radiation
electrodes of the feed radiation electrode; each of the non-feed
radiation electrodes is disposed along an outer edge of the
respective one of the plurality of branched radiation electrodes of
the feed radiation electrode; a space between adjacent ones of the
plurality of branched radiation electrodes gradually increases from
the common end to the open ends; each of the plurality of branched
radiation electrodes has a resonant frequency in a different
frequency band from the remaining one of the plurality of branched
radiation electrodes, and each of the plurality of non-feed
radiation electrodes has a resonant frequency in a different
frequency band from that of the remaining one of the plurality of
non-feed radiation electrodes, such that each of the plurality of
non-feed radiation electrodes disposed along and in the vicinity of
a respective one of the plurality of branched radiation electrodes
defines a double-resonance pair, and each of the double-resonance
pairs double-resonate at a frequency band that is different from
the remaining double-resonance pairs.
2. An antenna device according to claim 1, wherein each of the
plurality of non-feed radiation electrodes is disposed along and in
the vicinity of the respective one of the plurality of branched
radiation electrodes such that a space between the non-feed
radiation electrode and the respective branched radiation electrode
gradually increases from the common end to the open ends.
3. An antenna device according to claim 1, wherein the feed
terminal is connected to the common end of the plurality of
branched radiation electrodes.
4. An antenna device according to claim 1, wherein the plurality of
branched radiation electrodes have effective line lengths at which
the branched radiation electrodes are excited at different resonant
frequencies.
5. An antenna device according to claim 1, wherein three
strip-shaped electrodes extending from the bottom surface to the
top surface in parallel with each other are located on the same
side surface of the substrate, and the electrode of the three
strip-shaped electrodes disposed in the middle defines the feeding
terminal, and the other electrodes of the three strip-shaped
electrodes define the ground terminals.
6. An antenna device according to claim 1, wherein
capacitance-charging electrodes are provided on side-surfaces of
the substrate at the open ends of the plurality of branched
radiation electrodes.
7. An antenna apparatus comprising the antenna device defined in
claim 1, and a substantially rectangular circuit substrate, the
substrate of the antenna device is arranged near a corner of the
circuit substrate where two sides of the circuit substrate
intersect each other with one of the plurality of non-feed elements
being arranged along one of the two sides and another of the
plurality of non-feed elements being arranged along the other
side.
8. An antenna apparatus comprising a plurality of the antenna
device defined in claim 1, and a circuit substrate having the
plurality of antenna devices disposed thereon and including a
ground pattern connecting the ground terminals to each other and a
feeding pattern connecting the feeding terminals to a common signal
source.
9. An antenna apparatus according to claim 8, wherein filter
circuits are provided in paths of the feeding pattern which is
branched from the portion thereof connecting the feeding terminals
to the common signal source and extended toward the feeding
terminals, respectively.
10. An antenna device according to claim 1, wherein the plurality
of branched radiation electrodes includes two branched radiation
electrodes and the non-feed radiation electrodes are disposed on
both sides of and near the feed radiation electrode on the surface
of the substrate.
11. An antenna device according to claim 1, wherein the feeding
terminal is a feed electrode provided on a side-surface of the
substrate.
12. An antenna device according to claim 1, wherein the feeding
terminal is a terminal pin passing through the substrate.
13. Radio communication equipment comprising the antenna device
defined in claim 1, and a circuit substrate having an elongated
substantially rectangular shape with long and short sides; the
antenna device having a width substantially equal to the length of
one short side of the circuit substrate and being arranged along
one short side and both long sides of the circuit substrate; and
the open end of one of the non-feed radiation electrodes being
arranged along one of the two long sides of the circuit substrate,
and the open end of another of the non-feed radiation electrodes
being arranged along the other long side.
14. Radio communication equipment according to claim 13, wherein a
distal portion of the open end of one of the non-feed radiation
electrodes having the longest effective line length is arranged so
as to be close to the short side along which the antenna device is
arranged.
15. Radio communication equipment comprising the antenna device
defined in claim 1 and a circuit substrate including a
transmission-reception circuit for radio waves, each ground
terminal of the antenna device being connected to a ground terminal
of the circuit substrate, and the feeding terminal being connected
to an input-output terminal of the transmission-reception circuit.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna device, and more
particularly, to a multi-band antenna device and radio
communication equipment using the antenna device.
2. Description of the Related Art
Recently, portable telephones often include a dual band system
using two frequency bands, e.g., those of 800 to 900 MHz and 1800
to 1900 MHz. Reverse F-shaped antennas for receiving and
transmitting two frequency bands from a single antenna have been
proposed. For example, Japanese Unexamined Patent Application
Publication No. Hei, 10-93332 discloses an antenna has resonance
frequencies of 1500 MHz and 1900 MHz.
As shown in FIG. 15, this antenna includes a slit 2 provided in a
conductor plate 1 to define two radiation conductor plates 3 and 4
having different widths and lengths. A portion of the conductor
plate 1 is bent to form a connection conductor plate 5. The
radiation conductor plates 3 and 4 are supported on a ground
conductor plate 6 by the connection conductor plate 5. High
frequency power is supplied to the radiation conductor plates 3 and
4 via a feeding pin 7.
Moreover, the U.S. Pat. Nos. 6,271,794, 6,307,512 and 6,333,716
disclose an antenna in which two metallic patterns having different
electrical lengths are provided on the surface of a case for a
telephone to produce two radiation elements, such that the antenna
has resonance frequencies of 900 MHz and 1800 MHz. This antenna
includes a slit provided between the two metallic patterns to
enable adjustment of the bandwidths of the resonance
frequencies.
According to the examples of the prior art, each antenna is a dual
band antenna having two resonance frequencies in frequency bands
separated from each other, but has a single resonance
characteristic in each frequency band. Accordingly, the size of the
antenna must be increased to ensure a necessary bandwidth for each
resonance frequency. Thus the size of the antenna cannot be
reduced. Moreover, when frequency bands having a single resonance
are provided, respectively, the resonance characteristics have a
single peak. Thus, a wide frequency band cannot be achieved.
SUMMARY OF THE INVENTION
In order to overcome the above-described problems, preferred
embodiments of the present invention provide an antenna device
having a plurality of frequency bands and which achieves
double-resonance in the respective frequency bands.
Another preferred embodiment of the present invention provides
radio communication equipment including the antenna device having a
plurality of feed radiation electrode bands and double-resonance in
the respective frequency bands.
According to a first preferred embodiment of the present invention,
an antenna device is provided which includes a substrate made of a
dielectric or a magnetic material, a feed element including a
feeding terminal and a feed radiation electrode electrically
connected to the feeding terminal, and a plurality of non-feed
elements each including a ground terminal and a non-feed radiation
electrode electrically connected to the ground terminal, the feed
radiation electrode and the non-feed radiation electrodes are
arranged on the surface of the substrate such that the non-feed
radiation electrodes extend in the vicinity of and along the feed
radiation electrode.
When signal power is supplied to the feed terminal including a feed
electrode or a feeding pin, the feed element has at least one
resonance frequency. That is, when the feed element includes a
single feed radiation electrode resonates at the frequencies of the
fundamental wave and its higher-order harmonics which is determined
by the electrical length of the feed radiation electrode. Moreover,
the feed element, which includes a plurality of branched radiation
electrodes, is resonated at the resonance frequencies of the
respective branched radiation electrodes which are determined by
the effective line lengths of the branched radiation
electrodes.
When the non-feed radiation electrode of, e.g., the non-feed
radiation electrode positioned on the right side of the feed
element of the plurality of non-feed radiation electrodes has an
electrical line length greater than that of the non-feed radiation
electrode of the non-feed element positioned on the left side of
the feed element, and the feed element includes a single feed
radiation electrode, the non-feed radiation electrode on the right
side resonates at a resonance frequency near the frequency of the
fundamental wave. When the feed element includes a plurality of
branched radiation electrodes, the non-feed radiation electrode on
the right side resonates at a resonance frequency near the lowest
resonance frequency in the plurality of branched radiation
electrodes. The non-feed radiation electrode on the left side
having a smaller effective line length than that of the non-feed
radiation electrode on the right side resonates at a frequency near
one resonance frequency of the higher-order harmonics caused when
the feed element includes the single feed radiation electrode, or
resonates at a frequency near the highest resonance frequency in
the branched radiation electrodes.
Both of resonance frequencies adjacent to each other can be
provided, and also, matching of the double-resonance in the
respective frequency bands by the above-described operation of the
feed element and the non-feed elements is achieved. Moreover, the
resonance frequencies of the fundamental wave and its higher-order
harmonics of the feed element and the resonance frequencies of the
respective branched radiation electrodes are set in frequency bands
separated from each other. Thus, with one antenna, a plurality of
types of double-resonance is produced without mutual interference.
In addition, the bandwidths of the respective frequency bands are
greatly increased due to the double-resonance. The term
"double-resonance" means that the resonance frequencies of a feed
element and non-feed elements exist in the vicinity to each other,
and the bandwidth of a frequency band containing the resonance
frequencies is greatly increased.
Preferably, the feed radiation electrode includes a plurality of
branched radiation electrodes having the feeding terminal as a
common terminal.
According to the above-described preferred embodiment, the
effective line lengths of the plurality of branched radiation
electrodes are different from each other. Thereby, the feed element
has a plurality of resonance frequencies different from each other.
In other words, the resonance frequencies of the branched radiation
electrodes are set to be different from each other, and moreover,
the resonance frequencies of the branched radiation electrodes are
set in different frequency bands.
Preferably, the branched radiation electrodes have effective line
lengths at which the branched radiation electrodes are excited at
different resonance frequencies.
Therefore, the branched radiation electrodes are excited at
resonance frequencies independent of each other. Thus, resonance
frequencies are higher in the arrangement order of the branched
radiation electrodes, and also frequency bands different for the
resonance frequencies are set. For example, when the feed radiation
electrode includes two branched radiation electrodes, one resonance
frequency is set to a frequency band of 800 to 900 MHz which is
commonly used in portable telephones, and the other resonance
frequency is set to a frequency band of 1800 to 1900 MHz. Moreover,
one branched radiation electrode is excited by the fundamental wave
of the feed element, and the other branched radiation electrode is
excited by the higher-order harmonics of the fundamental wave such
as the double harmonic wave or the triple harmonic wave.
Preferably, the feed radiation electrode is defined by a single
radiation electrode, and the single radiation electrode has an
effective line length at which the single radiation electrode is
excited at the resonance frequency of the fundamental wave and the
resonance frequencies of the higher-order harmonics, caused by
feeding via the feeding terminal.
Accordingly, the feed radiation electrode has an effective line
length at which the electrode is resonated at the frequency of the
fundamental wave. The feed element has an electrical length at
which the element is resonated at the frequency of the fundamental
wave and the frequency obtained by multiplying the frequency of the
fundamental frequency by an integral number. Accordingly, by
setting the resonance frequency of the fundamental wave to the
lowest frequency of the used frequencies, the double or triple
harmonic wave of the fundamental wave is set to the other
frequency.
Also, preferably, each of the non-feed radiation electrodes extends
from the ground terminal with the other end thereof defining an
open end, each of the branched radiation electrodes extends from
the feeding terminal with the other end thereof defining an open
end, and the open-ends of the branched radiation electrodes are
arranged to be spaced from each other.
According to the above-described configuration, one branched
radiation electrode and the non-feed radiation electrode adjacent
to the branched radiation electrode defines a double resonance
pair. Moreover, by gradually increasing the width of a slit
provided in the plane of the feed radiation electrode to divide the
feed radiation electrode into the plural branched radiation
electrodes, the mutual interference between the double-resonance
pairs is greatly reduced, and matching of the double-resonance is
efficiently achieved.
Preferably, capacitance-charging electrodes are provided in the
open ends of the radiation electrodes on side-surfaces of the
substrate.
According to the above-described configuration, fringing capacities
(stray capacities) in the open ends of the respective radiation
electrodes define the open end capacities (electrostatic
capacities) between the capacitance-charging electrodes and the
ground patterns of the circuit substrate. Thus, the coupling
capacities between the feed element and the non-feed elements are
easily balanced, and adjustment is easily performed produce the
double-resonance in the same frequency band.
Preferably, the antenna device further includes a rectangular
circuit substrate, the substrate is arranged near one corner of the
circuit substrate where the two sides of the circuit substrate
intersect each other while one of the non-feed radiation electrodes
is arranged along one of the two sides, and the other non-feed
radiation electrode is arranged along the other side.
According to this configuration, ground patterns and wiring
patterns provided on the circuit substrate define paths for high
frequency currents, such that case-currents are excited along the
sides of the circuit substrate electric-field-coupled to the
respective non-feed elements. The case-currents cause the gains of
the non-feed elements, which are indirect-feed elements, to
increase substantially. Moreover, since the substrate of the
antenna device is arranged near the corner of the circuit
substrate, the electric field coupling between the non-feed
elements and the circuit substrate is reduced, such that the
electrical Q factor at resonance is greatly reduced. Thus, the
bandwidths of the frequency bands in which the double-resonance
occurs is greatly increased.
According to a second preferred embodiment of the present
invention, an antenna device is provided which includes a plurality
of antennas, and a circuit substrate having the plurality of
antennas disposed thereon, the plurality of antennas each include a
feed element having a feeding terminal and a feed radiation
electrode extending from the feeding terminal, and a non-feed
element having a ground electrode and a non-feed radiation
electrode extending from the ground electrode, the feed element and
the non-feed element are provided on a substrate, the feed
radiation electrode and the non-feed radiation electrode of each
antenna have effective line lengths different from each other, the
circuit substrate is provided with a ground pattern connecting the
ground electrodes to each other and a feeding pattern connecting
the feeding terminals to a common signal source.
Therefore, the circuit substrate is included as a portion of the
antenna device, and the electrical volume of the antenna device is
determined by the area of the circuit substrate. In particular,
when the size of the antenna device is increased to enhance the
transmission output, the size of the circuit substrate is simply
increased. Thus, the arrangement of the plurality of antennas on
the circuit substrate is determined based on the degree of the
mutual interference, performances required for the directivities of
the antennas, and other factors. Since the antennas are configured
to be double-resonated in different frequency bands, and a large
signal current flows through the feeding pattern, the transmission
output of the antenna device is greatly enhanced.
Preferably, filter circuits are provided in the paths of the
feeding pattern which is branched from the portion thereof
connecting the feeding terminals to the common signal source and
extended toward the feeding terminals, respectively.
According to the above-described configuration, signals outside of
the frequency bands in which the respective antennas are excited
are excluded. That is, only signals that excite the respective
antennas are supplied to the respective antennas. Accordingly,
separation between the frequency bands of the antennas is greatly
improved.
Preferably, non-feed radiation electrodes are provided on both
sides of and near the feed radiation electrode on the surface of
each substrate.
Since the non-feed radiation electrodes are provided on both sides
of each feed radiation electrode, each antenna is configured as an
antenna which is double-resonated in two frequency bands.
Accordingly, the antenna device includes at least four frequency
bands. Thus, the antenna device operates as a multi-band antenna by
setting the frequency bands to be different from each other.
The feeding terminal is preferably a feed electrode provided on a
side-surface of the substrate or a terminal pin passing through the
substrate, depending upon the required specifications.
According to the above-described configuration, the feeding
terminal configuration is selected from a variety of suitable
shapes. Particularly, the antenna device is configured as one of a
reversed L-shaped antenna and a reversed F-shaped antenna.
According to preferred embodiments of the present invention, radio
communication equipment is provided which includes one of the
above-described antenna devices, and a circuit substrate having an
elongated rectangular shape including long and short sides, the
antenna device has a width that is substantially equal to the
length of one short side of the circuit substrate and is arranged
along one short side and both long sides of the circuit substrate,
the open end of one of the non-feed radiation electrodes is
arranged to face the long side of the circuit substrate, and the
open end of the other non-feed radiation electrode is arranged to
face the other long side.
According to the radio communication equipment according to
preferred embodiments of the present invention, case-currents
occurring in two frequency bands are excited along the long sides
and the short side of the circuit substrate. Thereby, the gain of
the non-feed element arranged along the sides of the circuit
substrate is greatly enhanced. Moreover, since the open ends of the
two non-feed radiation electrodes arranged along the long sides and
the short side of the circuit substrate are opposite to each other,
the mutual interference between the adjacent non-feed elements is
greatly reduced, and the separation between the frequency bands is
greatly improved.
Moreover, since the three edges of the antenna device are
positioned near the ends of the circuit substrate, the
electric-field-coupling between the non-feed element arranged along
the ends of the circuit substrate and the circuit substrate is
reduced, such that the electrical Q factor of the double-resonant
characteristic is greatly reduced and the bandwidths of the
frequency bands are greatly increased. When the resonance frequency
of one of the frequency bands of the non-feed elements coincides
with the resonance condition of the case-current excited along the
sides of the circuit substrate, the gain at the resonance frequency
is greatly increased.
Preferably, in the radio communication equipment according to
preferred embodiments of the present invention, the feed radiation
electrode extends from the feeding terminal and includes an open
end, the non-feed radiation electrodes extend from the ground
terminals and include open ends, respectively, the open end at the
top of one non-feed radiation electrode having an effective line
length that is greater than the other non-feed radiation electrode
is arranged opposite to the direction in which the long side of the
circuit substrate extends so as to be spaced from the non-feed
radiation electrode.
According to the above-described configuration, the substrate edge
on the long-side side of the circuit substrate acts as an antenna
which operates in the lower frequency band of the antenna device.
Thus, the gain is increased. The gain of the antenna of a small
potable telephone is greatly enhanced at a frequency in the 800 to
900 MHz band.
According to preferred embodiments of the present invention, radio
communication equipment is provided which includes one of the
above-described antenna devices, and a circuit substrate including
a transmission-reception circuit for radio waves, each ground
terminal of the antenna device being connected to a ground terminal
of the circuit substrate, the feeding terminal being connected to
an input-output terminal of the transmission-reception circuit.
The radio communication device having the antenna device mounted
therein achieves multi-band communication in wide frequency
bands.
Other features, elements, characteristics and advantages of the
present invention will become more apparent from the following
detailed description of preferred embodiments thereof with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of the basic configuration of an
antenna device according to preferred embodiments of the present
invention.
FIG. 2 is a graph of the frequency characteristic showing the
return loss of the antenna device of FIG. 1.
FIG. 3A is a schematic plan view showing the basic configuration of
an antenna device according to preferred embodiments of the present
invention.
FIG. 3B is a schematic bottom view showing the basic configuration
of the antenna device according to preferred embodiments of the
present invention.
FIG. 4A is a perspective view showing the front-surface of an
antenna device according to a preferred embodiment of the present
invention.
FIG. 4B is a perspective view showing the back-surface of the
antenna device shown in FIG. 4A.
FIG. 5 is a plan view of another preferred embodiment of the
present invention in which the antenna device of FIGS. 4A and 4B is
mounted onto a circuit substrate for radio communication
equipment.
FIG. 6 is a plan view of another preferred embodiment of the
present invention in which the antenna device is mounted onto a
circuit substrate of radio communication equipment.
FIG. 7A is a perspective view showing the front surface of an
antenna device according to another preferred embodiment of the
present invention.
FIG. 7B is a perspective view showing the back surface of the
antenna device shown in FIG. 7A.
FIG. 8A is a perspective view showing the front surface of an
antenna device according to still another preferred embodiment of
the present invention.
FIG. 8B is a perspective view showing the back surface of the
antenna device shown in FIG. 8A.
FIG. 9A is a perspective view showing the front surface of an
antenna device according to yet another preferred embodiment of the
present invention.
FIG. 9B is a perspective view showing the back surface of the
antenna device shown in FIG. 9A.
FIG. 10 is a perspective view showing another configuration of the
feed terminal of an antenna device according to preferred
embodiments of the present invention.
FIG. 11A is a plan view showing still another configuration of the
feed terminal of the antenna device according to preferred
embodiments of the present invention.
FIG. 11B is a cross-sectional view taken along alternate long and
short dash line X--X in the antenna device of FIG. 11A.
FIG. 12A is a perspective view showing the front surface of an
antenna device according to another preferred embodiment of the
present invention.
FIG. 12B is a perspective view showing the back surface of one
single antenna used in the antenna device shown in FIG. 12A.
FIG. 12C is a perspective view showing the back surface of the
other single antenna used in the antenna device shown in FIG.
12A.
FIG. 13 is a perspective view showing another preferred embodiment
of the antenna device of FIG. 12A.
FIG. 14 is a plan view showing an antenna device according to still
preferred another embodiment of the present invention.
FIG. 15 is a perspective view of an antenna device of the related
art.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Hereinafter, preferred embodiments of the present invention will be
described with reference to the drawings. FIG. 1 shows the basic
configuration of an antenna device according to preferred
embodiments of the present invention. FIG. 2 shows the
characteristic curve of the antenna device of FIG. 1 which
illustrates the double resonance of the device. For simplification,
a preferred embodiment including two feed elements and two non-feed
elements will be described by way of an example.
In FIG. 1, a substrate 10 is formed of a dielectric material, and
has a rectangular surface. A feed element 11 is provided on the
surface of the substrate 10. A non-feed element 12 is provided on
the right side of the feed element 11 in the vicinity thereof.
Moreover, a non-feed element 13 is provided on the left side of the
feed element 11 in the vicinity thereof, and has a resonance
frequency different from that of the non-feed element 12.
The feed element 11 includes a feed radiation electrode 14 and a
feed terminal 15 connected to a feeding end 14a of the feed
radiation electrode 14. The feed radiation electrode 14 includes
branched radiation electrodes 16 and 17 which are branched into a
substantially Y-shape having the feeding end 14a in common, and
having lengths that are different from each other. The non-feed
elements 12 and 13 include strip-shaped non-feed radiation
electrodes 18 and 19, and ground ends 20 and 21 connected to ground
terminals 18a and 19a of the non-feed radiation electrodes 18 and
19, respectively.
The branched radiation electrodes 16 and 17 of the feed element 11
are configured such that the ends of the electrodes 16 and 17
opposite to the feeding end 14a define open ends 16b and 17b. The
branched radiation electrode 16 has an effective line length which
causes the electrode 16 to be excited at a resonance frequency f1.
The branched radiation electrode 17 has an effective line length
which causes the electrode 17 to be excited at a resonance
frequency f2. When a signal power is supplied to these branched
radiation electrodes 16 and 17 from a signal source 22 connected to
the feeding terminal 15 via an impedance matching circuit 23, the
feed element 11 is excited at the two resonance frequencies f1 and
f2 (f2>f1).
In other words, the feed element 11 has an electrical length which
includes that of the branched radiation electrode 16 and an
electrical length which includes that of the branched radiation
electrode 17. The branched radiation electrode 16 side of the feed
element 11 resonates at the resonance frequency f1, while the
branched radiation electrode 17 side of the feed element 11
resonates at the resonance frequency f2. The frequency bands in
which the resonance frequencies f1 and f2 occur are separated such
that no mutual interference occurs therebetween.
The sides opposite to the ground ends 18a and 19a of the non-feed
radiation electrodes 18 and 19 define open ends 18b and 19b,
respectively, similarly to the feed element 11. The non-feed
radiation electrodes 18 and 19 of the non-feed element 12 and 13
are excited by electromagnetic-field-coupling to the feed element
11. That is, the non-feed radiation electrode 18 of the non-feed
element 12 is electromagnetic-field-coupled primarily to the
branched radiation electrode 16 of the feed element 11. The
non-feed radiation electrode 19 of the non-feed element 13 is
electromagnetic-field-coupled primarily to the branched radiation
electrode 17 of the feed element 11.
In this case, the non-feed radiation electrode 18 of the non-feed
element 12 has an effective line length which is substantially
equal to that of the branched radiation electrode 16. The
electrical length of the non-feed element 12 including that of the
ground terminal 20 is less than that of the branched radiation
electrode 16 side of the feed element 11. The non-feed radiation
electrode 18 is excited at a frequency f3 near the resonance
frequency f1 of the branched radiation electrode 16 side of the
feed element 11.
The non-feed radiation electrode 19 of the non-feed element 13 has
an effective line length which is substantially equal to that of
the branched radiation electrode 17. The electrical length of the
non-feed element 13 including that of the ground terminal 21 is
less than that of the branched radiation electrode 17 side of the
feed element 11. The non-feed radiation electrode 19 is excited at
a frequency f4 near the resonance frequency f2 of the branched
radiation electrode 17 side. The impedance matching circuit 23
matches the impedance of the feed radiation electrode 14 with that
of the signal source 22.
In the above-described configuration, the effective line lengths of
the branched radiation electrode 16 and the non-feed radiation
electrode 18 are set such that the electrodes 17 and 19 are excited
in a common frequency band, for example, in the frequency band of
800 to 900 MHz. Moreover, the effective line lengths of the
branched radiation electrode 16 and the non-feed radiation
electrode 18 are set such that the electrodes 16 and 18 are excited
in a frequency band higher than the resonance frequency f1 of the
branched radiation electrode 16, for example, in the frequency band
of 1800 to 1900 MHz.
The interval between the side edges opposed to each other of the
branched radiation electrodes 16 and 17 of the feed radiation
electrode 14 is gradually increased toward the open ends 16b and
17b. This prevents deterioration of the resonance characteristic
which is caused by the mutual interference of the
electric-field-coupling. Moreover, the non-feed radiation
electrodes 18 and 19 are disposed in the vicinities of the branched
radiation electrodes 16 and 17, respectively. Referring to the
intervals between the side-edges opposed to each other of the
branched radiation electrode 16 and the non-feed radiation
electrode 18 and between those of the branched radiation electrode
17 and the non-feed radiation electrode 19, the intervals between
the feeding end 14a of the feed radiation electrode 14 and the
ground end 18a of the non-feed radiation electrode 18 and between
the feeding end 14a and the ground end 19a of the non-feed
radiation electrode 19 are set to be greater than the intervals
between the open end 16b of the branched radiation electrode 16 and
the open end 18b of the non-feed radiation electrode 18 and between
the open end 17b of the branched radiation electrode 17 and the
open end 19b of the non-feed radiation electrode 19, respectively.
Thus, excessive electric field coupling between the feed element 11
and the non-feed elements 12 and 13 is controlled,
respectively.
According to the above-described configuration, when a transmission
signal is supplied from the signal source 22 to the feed radiation
electrode 14, the branched radiation electrodes 16 and 17 of the
feed element 11 are excited at the resonance frequencies f1 and f2,
respectively. At this time, the non-feed elements 12 and 13 are
electromagnetic field coupled to the feed element 11. With the
above-described electrode arrangement of the feed element 11 and
the non-feed elements 12 and 13, the magnetic-field-coupling
between the feeding terminal 15 side of the feed element 11 and the
ground terminal 20 side of the non-feed radiation electrode 18 and
between the feeding terminal 15 side of the feed element 11 and the
ground terminal 21 side of the non-feed radiation electrode 19, and
also, the electric-field-coupling between the open end 16b side of
the branched radiation electrode 16 and the open end 18b side of
the non-feed radiation electrode 18 and between the open end 17b of
the branched radiation electrode 17 and the open end 19b of the
non-feed radiation electrode 19 are adjusted.
Thus, the branched radiation electrode 16 and the non-feed
radiation electrode 18 have include both of the resonance
frequencies f1 and f3, and the frequencies f1 and f3 are near each
other. For example, the branched radiation electrode 16 and the
non-feed radiation electrode 18 are double-resonated in a frequency
band of 800 to 900 MHz. Referring to the resonance frequency f2 of
the branched radiation electrode 17 and the resonance frequency f4
of the non-feed radiation electrode 19, similarly, the branched
radiation electrode 17 and the non-feed radiation electrode 19 are
double-resonated at the frequencies f2 and f4 higher than the
resonance frequencies f1 and f3 of the branched radiation electrode
16 and the non-feed radiation electrode 18, respectively. For
example, the branched radiation electrode 17 and the non-feed
radiation electrode 19 are double-resonated in a frequency band of
1800 to 1900 MHz.
FIGS. 3A and 3B shows another preferred embodiment of the antenna
device of the present invention. The same components as those in
the preferred embodiment of FIG. 1 are designated by the same
reference numerals. The repeated description of the same components
is omitted. In this preferred embodiment, the feed radiation
electrode 14 of the feed element 11 includes three branched
radiation electrodes 16, 17, and 24.
In FIGS. 3A and 3B, the feed element 11 includes the feed radiation
electrode 14 having the three branched radiation electrodes 16, 17,
and 24. That is, in the configuration of the feed radiation
electrode 14, the branched radiation electrodes 16, 17, and 24
having different lengths are branched from the common feeding end
14a to form a substantially W-shape. More particularly, the
interval between the branched radiation electrodes 16 and 17 shown
in FIG. 1 is increased. The third branched radiation electrode 24
is provided in the middle of the branched radiation electrodes 16
and 17.
The branched radiation electrode 24 has an effective line length
which is between those of the branched radiation electrodes 16 and
17, and is excited at a resonance frequency f5 which is in a
frequency band separated from the frequency bands of the branched
radiation electrodes 16 and 17 (f2>f5>f1). Thus, the feed
element 11 includes three electrical lengths, and includes
resonance frequencies f1, f2, and f5 in the three frequency
bands.
A non-feed element 25 which is paired with the branched radiation
electrode 24 to be double-resonated is provided on the back surface
of the substrate 10. That is, a non-feed radiation electrode 25a is
provided on the back surface of the substrate 10 so as to extend
along the branched radiation electrode 24. The non-feed radiation
electrode 25a is configured in the same manner as the non-feed
radiation electrodes 18 and 19. The ground end of the electrode 25a
is connected to the ground terminal.
The non-feed radiation electrode 25a is
electromagnetic-field-coupled to the branched radiation electrode
24, has an effective line length substantially equal to that of the
branched radiation electrode 24, and is excited at a frequency f6
near the resonance frequency f5 of the branched radiation electrode
24. The branched radiation electrode 24 and the non-feed radiation
electrode 25a are double-resonated in the same frequency band as
that of the resonance frequencies f5 and f6. This frequency band is
separated from the frequency bands of the resonance frequencies f3
and f4 of the non-feed element 12 and 13. The non-feed radiation
electrodes 18 and 19 of the non-feed elements 12 and 13 are
provided on the back surface of the substrate 10 similarly to the
non-feed radiation electrode 25a. Thereby, the size of the
substrate 10 is greatly reduced.
FIGS. 4A, 4B, and 5 show an antenna device according to a first
preferred embodiment of the present invention. FIGS. 4A and 4B show
the antenna device, and FIG. 5 shows the antenna device mounted on
a circuit substrate. This preferred embodiment is described using
two feed elements and two non-feed elements.
Referring to FIGS. 4A and 4B, the antenna device includes a
substrate 26 having a rectangular front surface 26e. The substrate
26 is made of a dielectric such as a ceramic material, a resin
material, or other suitable dielectric material, or a magnetic
material. The antenna device includes a top plate 27 having the
flat surface 26e, two plate-shaped legs 28 and 29 provided along
the short-edges 26a and 26b of the top plate 27 on both sides
thereof in the longitudinal direction, and a center leg 30 in the
approximate center of the top plate 27 and in parallel to the both
legs 28 and 29. These legs 28, 29, and 30 are formed integrally
with the top plate 27.
A feed element 31 and two non-feed elements 32 and 33 on both sides
of the feed element 31 are provided on the top surface 26e of the
substrate 26. Three strip electrodes 36, 37, and 38 are provided at
a desired interval on the side-surface (leg side surface) on one
short-edge side of the substrate 26. The strip electrodes 36, 37,
and 38 extend in parallel to each other, in the direction from the
bottom surface to the top surface 26e of the substrate 26 (vertical
direction), positioned near one end in the side-surface in the
short-edge direction. The center electrode defines a feed electrode
36, and the electrodes on the right and left sides define first and
second ground electrodes 37 and 38, respectively. The lower end
portions of these electrodes are bent to extend on the bottom 28a
of the leg 28 to define feeding terminals 36a and ground terminals
37a and 38a, respectively.
The upper end of the feed electrode 36 is connected to a feed
radiation electrode 40 provided on the top surface 26e of the
substrate 26. The feed radiation electrode 40 is configured to
gradually extend from the feed electrode 36 toward the corner on
the left side of the top surface 26e. Moreover, the feed radiation
electrode 40 includes an elongated triangular slit 40a gradually
extending toward the corner which is provided in the plane of the
electrode 40, such that two branched radiation electrodes 41 and 42
are provided.
In particular, the first branched radiation electrode 41 gradually
extends from the vicinity to the feed electrode 36 toward the other
short edge 26b of the top surface 26e of the substrate 26. The
short edge 26b is an open end 41a of the electrode 41. The second
branched radiation electrode 42 which is adjacent to the first
branched radiation electrode 41 with the slit 40a being interposed
between them, gradually extends from the vicinity of the feed
electrode 36 toward the long-edge 26d on the left side which
extends in the longitudinal direction of the substrate 26. The end
of the electrode 42 defines an open end 42a. In this configuration,
the first branched radiation electrode 41 has an effective line
length greater than that of the second branched radiation electrode
42.
Two non-feed radiation electrodes 43 and 44 are provided on both
sides of and close to the feed radiation electrode 40. In
particular, the first non-feed radiation electrode 43 is disposed
at a distance from and on the right side of the first branched
radiation electrode 41, and has a quadrangle shape extending from
the upper end of the first ground electrode 37, that is, from the
short edge 26a to the opposed short edge 26b. A slit 43a is
provided in the plane of the first non-feed radiation electrode 43
so as to extend from the short edge 26a in parallel to the right
long-edge 26c. The long edge 26c defines an open end 43b, and the
open end 43c at the top is on the short edge 26a which lies on the
first ground electrode 37 side.
The second non-feed radiation electrode 44 is provided on the left
side of and at a distance from the second branched radiation
electrode 42, and extends from the short-edge 26a on the second
ground electrode 38 side to the left long-edge 26d, which defines
an open end 44a, forming a triangular shape. In this configuration,
the effective line length of the second non-feed radiation
electrode 44 is less than that of the first non-feed radiation
electrode 43. Referring to the intervals between the feed radiation
electrode 40 and the non-feed radiation electrodes 43 and 44, the
intervals between them on the open end 41a and 42a side are greater
than the intervals between the feed electrode 36 and the ground
electrodes 37 and 38, respectively. Thereby, the intensity of the
electric-field-coupling between the feed element 31 and the
non-feed elements 32 and 33 is adjusted.
A strip-shaped capacitance-charging electrode 48 is provided on the
side-surface 35 on the short-edge side which is opposite to the
side surface 34 of the substrate 26 having the feed electrode 36
provided thereon. The electrode 48 connected to the open end 41a of
the first branched radiation electrode 41 extends vertically from
the short-edge 26b. The lower end of the capacitance-charging
electrode 48 is opposed to a fixed ground electrode 52 at a desired
interval. Thus, an open end capacity is provided between the
capacitance-charging electrode 48 and the fixed electrode 52.
Moreover, a capacitance-charging electrode 49 is provided on the
side-surface 47 on the long-edge 26d side of the substrate 26. The
electrode 49 connected to the open end 42a of the second branched
radiation electrode 42 vertically extends on the side surface of
the center leg 30. Furthermore, a capacitance-charging electrode 51
is provided on the side surface 47 on the long-edge side, using the
side surface of the leg 28. The electrode 51 connected to the open
end 44a of the second non-feed radiation electrode 44 extends
vertically from the long-edge 26d.
Similarly, capacitance-charging electrodes 50 are provided on the
side surface 46 on the long-edge side opposite to the side surface
47 of the substrate 26. The electrodes 50 connected to the open end
43b of the first non-feed radiation electrode 43 extend vertically
on the side surfaces of the three legs 28, 29, and 30. Furthermore,
fixed electrodes 52 and 53 for fixing the antenna device onto a
circuit substrate, which will be described later, are provided in
the lower portions of the side surfaces 34 and 35 on the short-edge
side and are bent to extend on the bottoms of the legs 28 and 29,
respectively.
The above-described antenna device is mounted onto a circuit
substrate 55 for radio communication equipment, as shown in FIG. 5.
The antenna device is disposed such that the feed electrode 36 is
directed toward the short side 55a of the circuit substrate 55.
Moreover, the device is positioned near the corner of the circuit
substrate 55 with the short edge 26a and the long edge 26c of the
substrate 26 elongating along the short side 55a and the long side
55c of the circuit substrate 55, respectively.
In particular, the open end 43b of the non-feed radiation electrode
43 of the non-feed electrode 32 is adjacent to the long side 55c of
the circuit substrate 55. The open end 43c at the top is adjacent
to the short side 55a of the circuit substrate 55 from which the
feed electrode 36 extends. The direction of the open end 43c bent
by the slit 43a is opposite to the direction in which the long side
55c of the circuit substrate 55 extends, with respect to the feed
electrode 36 of the antenna device. In other words, the open end
43c is opposite to the short side 55b which is opposed to the short
side 55a.
The open end 44a of the non-feed radiation electrode 44 of the
non-feed electrode 33 faces the other long-side 55d of the circuit
substrate 55 which is opposed to the long-side 55c thereof. The
direction of the open end 44a is the same as that in which the
short side 55a extends, with respect to the feed electrode 36
side.
On the circuit substrate 55 on which the antenna device is disposed
as described above, ground patterns are provided at the mounting
positions for the antenna device, excluding wiring patterns which
are connected to the feeding terminal 36a and function as the
input-output terminal of a transmission-reception circuit not shown
in the drawing, and also, wiring patterns for mounting other
circuit components, such as impedance matching circuits and their
peripheries. The bottoms 26a, 29a, and 30a of the legs 28, 29, and
30 provided on the substrate 26 of the antenna device are fixed
thereon.
That is, the feeding terminal 36a are soldered to the input-output
terminals of the transmission-reception circuits. The ground
terminals 37a and 38a and the fixed electrodes 52 and 53 are
soldered to the ground patterns. Elastic pins having spring
properties may be used instead of the soldering. The tips of the
capacitance-charging electrodes 48, 49, 50, and 51 are opposed to
the ground patterns. Open end capacities are provided between the
capacitance-charging electrodes 48, 49, 50, and 51 and the ground
patterns. The circuit substrate 55 is defined by a single layer
substrate or a laminated circuit substrate. The wiring patterns are
defined by transmission-reception circuits for use with radio waves
and signal processing circuits for base bands or other suitable
circuits.
According to the above-described configuration, when signal power
is supplied to the feeding electrode 36 via the impedance matching
circuit, the feed element 31 is excited at the two resonance
frequencies f1 and f2. That is, the first branched radiation
electrode 41 having a greater effective line length is excited at
the resonance frequency f1 which lies in the frequency band of,
e.g., 800 to 900 MHz. The second branched radiation electrode 42
having a lesser effective line length is excited at the resonance
frequency f2 which is higher than the resonance frequency f1 and
lies in the frequency band of, e.g., 1800 to 1900 MHz.
The electric-field-coupling between the first and second branched
radiation electrodes 41 and 42 is reduced, due to the slit 40a
having an increased width in the directions of the open ends 41a
and 42a, and the capacitance coupling between the
capacitance-charging electrodes 48 and 49 and the ground patterns
is suitably set. Thereby, the two resonance frequencies f1 and f2
occur independently of each other. In other words, the feed element
31 has two resonance characteristics which are independent of each
other, caused by the electrical lengths which are determined by the
two branched radiation electrodes 41 and 42, the two
capacitance-charging electrodes 48 and 49, and the feed electrode
36.
The non-feed element 32 is electromagnetic-field-coupled to the
feed element 31 such that excitation power is supplied to the
element 32. In other words, the non-feed element 32 is excited at
the resonance frequency f3, caused primarily by the current
(magnetic field) coupling between the feeding electrode 36 and the
ground electrode 37, the electric-field-coupling between the
non-feed radiation electrode 43 and the first branched radiation
electrode 41, and the capacitance coupling between the three
capacitance-charging electrodes 50 and the ground patterns. The
resonance frequency f3 is in the same frequency band as the
resonance frequency f1 of the first branched radiation electrode
41, that is, in the frequency band of, e.g., 800 to 900 MHz.
In this case, the non-feed radiation electrode 43 is excited at the
resonance frequency f3 which is lower than the resonance frequency
f1 of the first branched radiation electrode 41. Thus, the feed
element 31 and the non-feed element 32 are double-resonated at the
resonance frequencies f1 and f3. The width of the frequency band in
which the feed element 31 and the non-feed element 32 are
double-resonated is greater as compared to the resonance
characteristics for the resonance frequencies f1 and f3.
A case-current is excited along the long side 55c of the circuit
substrate 55, due to the resonance current which flows toward the
open end 43c at the top of the non-feed radiation electrode 43. The
case-current increases the gain of the non-feed element 32 when the
length of the long side 55c of the circuit substrate 55 is
approximately half (.lambda./2) of the wavelength .lambda. of a
used radio wave. Therefore, preferably, the length of the long side
55c of the circuit substrate 55 is substantially equal to the
wavelength at the resonance frequency at which a high gain is
achieved.
Moreover, since the first non-feed radiation electrode 43 is
disposed near the long side 55c of the circuit substrate 55, the
electric coupling between the open ends 43b and 43c and the ground
patterns is reduced, such that the electrical Q factor of the
resonance characteristic is decreased, and the frequency bandwidth
is greatly increased.
Similarly, the non-feed element 33 is electromagnetic-field-coupled
to the feed element 31 such that excitation power is supplied to
the element 33. In other words, the non-feed element 33 is excited
at the resonance frequency f4, caused primarily by the current
(magnetic field)-coupling between the feeding electrode 36 and the
ground electrode 38, the electric-field-coupling between the second
non-feed radiation electrode 44 and the second branched radiation
electrode 42, and the capacitance coupling between the
capacitance-charging electrode 51 and the ground pattern. The
resonance frequency f4 is in the same frequency band as the
resonance frequency f2 of the second branched radiation electrode
42, that is, in the frequency band of, e.g., 1800 to 1900 MHz.
The non-feed radiation electrode 44 is excited at the resonance
frequency f4 which is less than the resonance frequency f2 of the
second branched radiation electrode 42. Thus, the feed element 31
and the non-feed element 33 are double-resonated at the resonance
frequencies f2 and f4. The width of the frequency band in which the
feed element 31 and the non-feed element 33 are double-resonated is
greater as compared to the resonance characteristics of the single
resonance frequencies f2 and f4. Then, a case-current is excited
along the short side 55a of the circuit substrate 55, due to the
resonance current which flows toward the open end 44a of the second
non-feed radiation electrode 44.
The case-current increases the gain of the non-feed element 33.
Moreover, since the second non-feed radiation electrode 44 is
disposed near the short side 55a of the circuit substrate 55, the
electric-field-coupling between the open end 44a and the ground
pattern is decreased, and the electrical Q factor of the resonance
characteristic is reduced. Thus, a wide frequency band is provided.
As a result, the frequency bandwidth of the double-resonance
characteristic is greatly increased.
The combination of the first branched radiation electrode 41 of the
feed element 31 and the non-feed radiation electrode 43 defines a
first double-resonant pair which provides a first frequency band.
The combination of the second branched radiation electrode 42 and
the second non-feed radiation electrode 44 defines a second
double-resonant pair which provides a second frequency band
separated from the first frequency band and being higher than the
first frequency band. Accordingly, the antenna device is
double-resonated in at least one of the frequency bands to produce
a resonance characteristic having two peaks. Thus, the antenna
device functions as a dual band antenna having a wide frequency
band.
Referring to the substrate 26, the top plate 27 is supported by the
legs 28, 29, and 30. Thus, the weight of the substrate 26 is
greatly reduced. Moreover, for example, a circuit defining a
portion of the transmission-reception circuit is arranged in the
space between the center leg 30 and the legs 28 and 29 on both
sides of the center leg 30. The thickness of the top plate 27 is
less than the height of the legs 28, 29, and 30. Thus, the
effective dielectric constant of the substrate 26 is greatly
reduced, irrespective of the height of the substrate 26.
Accordingly, excessive electric field coupling between the feed
element 31 and the non-feed elements 32 and 33 is efficiently
controlled, and the antenna characteristic is greatly improved.
An antenna device according to a second preferred embodiment of the
present invention will be described with reference to FIGS. 6, 7A,
and 7B. The same elements as those in the first preferred
embodiment of FIGS. 4A and 4B are designated by the same reference
numerals. The repeated description is omitted. The antenna device
according to second preferred embodiment has a width that is
substantially equal to one of the short sides of a substrate.
Referring to FIG. 6, a circuit substrate 56 to be incorporated into
the case of a portable telephone is configured such that the ratio
in length of the long sides 56c and 56d to the short sides 56a and
56b is in the range of about 2 to about 4. The substrate 57 of the
antenna device is mounted on the circuit substrate 56, in which a
long edge 57c of the substrate 57 is arranged along one short side
56a of the circuit substrate 56, and the short edges 57a and 57b
are arranged along the long sides 56c and 56d of the circuit
substrate 56. The length of the long edges 57c and 57d of the
substrate 57 is equal to or slightly less than that of the short
sides 56a and 56b of the circuit substrate 56.
The substrate 57 has a box-like shape in which an opening 58a is
provided on the bottom 58. The thickness of the top plate 60 is
less than the height of the side wall 59. A feed element 61 and
non-feed elements 62 and 63 are provided on the front surface 60a
of the substrate 57, similarly to the first preferred embodiment of
FIGS. 4A and 4B. The feeding electrode 36 and the ground electrodes
37 and 38 of the feed element 61 and the non-feed elements 62 and
63 are provided on a wall 59c on the long-edge side of the
substrate 57, near one end in the longitudinal direction of the
wall.
The non-feed radiation electrode 43 connected to the upper end of
the ground electrode 37 extends from a long edge 57c to the
opposite long edge 57d. Open ends 43b and 43d divided by the slit
43a are connected to capacitance-charging electrodes 50 provided on
the wall 59a on the right short-edge side of the substrate 57. On
the other hand, the non-feed radiation electrode 44 connected to
the ground electrode 38 extends along a long edge 57c to a right
short-edge 57b, and the open end 44a is connected to the
capacitance-charging electrode 51 provided on the wall 59b on the
short-edge 59b.
The feed radiation electrode 40 defining the feed element 61, that
is, the branched radiation electrodes 41 and 42 are provided
between the non-feed radiation electrodes 43 and 44, similarly to
the first preferred embodiment of FIGS. 4A and 4B. The open end 41a
is connected to the capacitance-charging electrode 48 provided on
the wall 59d on one long-edge side. The open end 42a is connected
to the capacitance-charging electrode 49 provided on the wall 59b
on the other short-edge side.
In the above-described configuration, the first branched radiation
electrode 41 and the non-feed radiation electrode 43 are radiation
electrodes defining a double-resonant pair, and are
double-resonated, e.g., in a frequency band of 800 to 900 MHz.
Moreover, the second branched radiation electrode 42 and the
non-feed radiation electrode 44 are radiation electrodes which are
double-resonated, e.g., in a frequency band of 1800 to 1900 MHz,
and define a double-resonant pair.
The open end 43b of the non-feed radiation electrode 43 is arranged
along the long side 56c of the circuit substrate 56, and the open
end 43c at the top of the electrode 43 is arranged opposite to the
direction in which the long side 56c extends (opposite to the
direction of the short side 56b). That is, the open end 43c is
positioned in the long edge 57c on the short-side 56a side in the
vicinity of the ground electrode 37. Accordingly, case-current in
the lower frequency band is excited along the long side 56c of the
circuit substrate 56. This greatly improves the gain of the
antenna.
Similarly, the non-feed radiation electrode 44 which functions in
the higher frequency band is arranged along the short side 56a of
the circuit substrate 56, and extends in the same direction as the
short side 56a. The open end 44a is provided in the short-edge 57b
which is on the long-side 56d side of the circuit substrate 56.
Accordingly, case-current in the high frequency side, that is,
having a frequency band of 1800 to 1900 MHz is excited on the edge
of the substrate which is on the short-side 56a side of the circuit
substrate 56. This greatly enhances the gain in the high frequency
band.
Referring to the above-described excitation of the case-current,
the non-feed radiation electrodes 43 and 44 are arranged in the end
of the circuit substrate 56. Thereby, the electric field coupling
between the non-feed radiation electrodes 43 and 44 and the circuit
substrate 56 is reduced. Thus, the electrical Q factor of the
resonance characteristic does not increase substantially, and
moreover, the bandwidth is greatly increased. Moreover, the open
end 43b of the non-feed radiation electrode 43 is provided on the
long-side 56c side of the circuit substrate 56. The open end 44a of
the non-feed radiation electrode 44 is provided on the long-side
56d side of the circuit substrate 56. Thus, the open ends 43b and
44a are spaced from each other. Thus, the mutual interference
between the two double-resonant pairs is greatly reduced, and
deterioration of the double-resonance characteristic is
prevented.
FIGS. 8A and 8B show a third preferred of the antenna device shown
in FIGS. 7A and 7B. The same elements as those in the second
preferred embodiment of FIGS. 7A and 7B are designated by the same
reference numerals. The repeated description is omitted. The third
preferred embodiment includes a slit 40a provided in the feed
radiation electrode 40 that is significantly enlarged.
Referring to FIGS. 8A and 8B, the feed electrode 36 and the ground
electrodes 37 and 38 are provided on the wall 59c on one long-edge
side of the substrate 57 in the approximate middle in the
longitudinal direction of the wall 59c, similarly to the second
preferred embodiment of FIGS. 7A and 7B. The branched radiation
electrode 41 extends from the long edge 57c toward the corner at
the right end of the long edge 57d opposed to the long edge 57c,
has the open end 41a in the long edge 57d and the short edge 57a,
and is connected to a capacitance-charging electrode 66 provided on
the long-edge wall 59d of the substrate 57, and also the
capacitance-charging electrode 48 provided on the short-edge wall
59a of the substrate 57. The top of the capacitance-charging
electrode 66 is opposed to a fixed electrode 78 at a desired
interval therebetween.
On the other hand, the branched radiation electrode 42 extends
toward the corner at the left end of the long edge 57b, has the
open end 42a on the long edge 57d and the short edge 57b, and is
connected to a capacitance-charging electrode 67 provided on the
long-edge wall 59d and also the capacitance-charging electrode 49
provided on the short-edge wall 59b. The top of the
capacitance-charging electrode 67 is opposed to a fixed electrode
69 at a desired interval therebetween, similarly to the branched
radiation electrode 41.
The slit 40a, which separates the branched radiation electrodes 41
and 42 from each other, widens from the feed electrode 36 side
toward the long-edge 57d gradually and significantly. Thereby, the
mutual interference between the two resonance frequencies of the
branched radiation electrodes 41 and 42 is greatly reduced. In
other words, the mutual interference between the double-resonant
pair including the branched radiation electrode 41 and the non-feed
radiation electrode 43 and the double-resonant pair including the
branched radiation electrode 42 and the non-feed radiation
electrode 44 is greatly reduced.
The non-feed radiation electrode 43 extends toward the right
short-edge 57a, and the open ends 43b and 43c are positioned on the
short edge 57a and the long edge 57c, respectively. The open end
43b is connected to the two capacitance-charging electrodes 50. The
non-feed radiation electrode 44 extends toward the left short-edge
57b. The open end 44a positioned on the short edge 57b is connected
to the two capacitance-charging electrodes 51 provided on the
short-side wall 59b.
According to the above-described configuration, the open ends 41a
and 42a of the two branched radiation electrodes 41 and 42 are
separated from each other as much as possible. Thus, the
band-separation between the two double-resonant pairs is greatly
improved, and the characteristics of the respective double-resonant
pairs are greatly improved. The antenna device is mounted on the
circuit substrate 56 in a similar manner to that shown in FIG. 6,
and case-current is excited along the sides 56a and 56c of the
circuit substrate 56, similarly to the preferred embodiment of FIG.
6. Thus, the gain of the respective double-resonant pairs is
greatly improved.
FIGS. 9A and 9B show an antenna device according to a fourth
embodiment of the present invention. The same elements as those in
the first preferred embodiment of the FIGS. 4A and 4B are
designated by the same reference numerals. The repeated description
is omitted. The fourth embodiment is featured in that the feed
element includes a single feed radiation electrode.
In FIGS. 9A and 9B, a feed element 71 includes a single feed
radiation electrode 72 having a feeding end 72a which is the upper
end of the feed electrode 36. A plurality of slits 72b are provided
in the plane of the feed radiation electrode 72 to extend from the
side-edges in the extension direction of the feed radiation
electrode 72, and thereby, the effective line length of the feed
radiation electrode 72 is appropriately set. The
capacitance-charging electrode 48 provided on the short-edge wall
35 is connected to the open end 72c of the feed radiation electrode
72. Moreover, a capacitance-charging electrode 73 provided on the
long-edge wall 47 is connected to the open end 72c. An
electrostatic capacity is generated between the
capacitance-charging electrode 48 and the fixed electrode 52. Also,
an electrostatic capacity is generated between the
capacitance-charging electrode 73 and the ground pattern.
The feed element 71, when signal power is supplied thereto via the
feeding electrode 36, is excited at the resonance frequency of the
fundamental wave and also at the resonance frequencies of the
higher-order harmonics such as the double or triple harmonic wave.
The resonance frequency of the fundamental wave is in the same
frequency band as that of the non-feed element 32. Thus, the feed
element 71 and the non-feed radiation electrode 32 are
double-resonated. The resonance frequencies of the higher-order
harmonics of the feed element 71 are in the same frequency band as
the resonance frequency of the non-feed element 32. The feed
element 71 and the non-feed element 33 are double-resonated at
higher resonance frequencies than that of the non-feed element 32.
In the above-described fourth preferred embodiment, the fundamental
wave and the higher-order harmonics of the feed radiation electrode
72 are set with the slits 72b. However, this is not
restrictive.
In any of the above-described preferred embodiments, the feed
radiation electrodes 40 and 72 are connected to the feed electrode
36. The upper end of the feeding electrode 36 may be separated from
the feed radiation electrodes 40 and 72 to provide a predetermined
interval (gap) for capacitance-coupling.
Moreover, as shown in FIG. 10, a feed electrode 74 is provided on
the side-surface of a substrate 75 which is on the open-ends 41a
and 42a side of the branched radiation electrodes 41 and 42. The
tip of the feed electrode 74 is provided near the open ends 41a and
42a at a desired interval therebetween to be capacitance-coupled to
the branched radiation electrodes 41 and 42. In this feeding
configuration, the base end 40b of the branched radiation
electrodes 41 and 42 is grounded via a ground electrode. In other
words, the feeding electrode 36 in the above-described preferred
embodiments defines the ground electrode.
Moreover, as shown in FIGS. 11A and 11B, a feeding pin passing
through the top plate 27 of the substrate 26 is provided in the
position of the base portion of the branched radiation electrodes
41 and 42 which is equivalent to about 50 .OMEGA., such that signal
power is supplied to the branched radiation electrodes 41 and 42
via the feeding pin 76. The lower end of the feeding pin 76 is
connected to a feeding pattern 77 provided on the circuit substrate
55. The feed configuration of FIGS. 11A and 11B is the same as that
of FIGS. 4A and 4B except that the feed electrode 36 defines the
ground electrode.
FIGS. 12A and 12B show an antenna device according to a fifth
preferred embodiment of the present invention. This antenna device
includes two single antennas that are mounted on a circuit
substrate to define an antenna for use in dual bands.
Referring to FIGS. 12A and 12B, two single antennas 81 and 82 are
mounted at a desired interval therebetween on a circuit substrate
80. These single antennas 81 and 82 are provided with feed elements
83 and 84 and non-feed elements 85 and 86 provided on substrates 87
and 88, respectively. The feed elements 83 and 84 are arranged
adjacent to each other. The non-feed elements 85 and 86 are
disposed on the outer side of the feed elements 83 and 84,
respectively. The configurations of the substrates 87 and 88 are
the same as that of FIGS. 7A and 7B, respectively.
The single antenna 81 is provided with a feed electrode 89 and a
ground electrode 91 extending vertically on the side-surface on one
short-edge side of the substrate 87. The feed electrode 89 and the
ground electrode 91 are arranged in the vicinity of each other, in
which the feed electrode 89 is located on the left side and the
ground electrode 91 is located on the right side. A non-feed
radiation electrode 95 connected to the upper end of the ground
electrode 91 is provided on the front surface of the substrate 87
so as to extend at a constant width, in the longitudinal direction
of the substrate 87, and is configured in the same manner as in
FIGS. 4A and 4B. The open end of the electrode 95 is connected to a
capacitance-charging electrode 97 provided on the side surface on
one long-edge side of the substrate 87.
On the other hand, the feed radiation electrode 93, which is
provided on the substrate 87, extends from the upper end of the
feed electrode 89 in the longitudinal direction of the substrate
87, gradually bending so as to be spaced further from the non-feed
radiation electrode 95. The open end of the feed radiation
electrode 93 is connected to a capacitance-charging electrode 98
which is provided on the side surface on the long-edge facing the
single antenna 82, at a location relatively near the feed electrode
89. A slit 93a is provided in the plane of the feed radiation
electrode 93 so as to extend from the feed electrode 89 side, and
thereby, the effective line length of the feed radiation electrode
93 is adjusted.
In the single antenna 82, a feed electrode 90 and a ground
electrode 92 are provided on the side surface on one short-edge
side of the substrate 88, in which the feed electrode 90 is located
on the right side, and the ground electrode 92 is located on the
left side, similarly to the single antenna 81. On the surface of
the substrate 88, a non-feed radiation electrode 96 connected to
the upper end of the ground electrode 92 extends at a constant
width, along the left side of the substrate 88 in the longitudinal
direction of the substrate 88. The open end at the top of the
electrode 96 is connected to a capacitance-charging electrode 99
provided on the side surface on the long-edge side of the substrate
88.
A feed radiation electrode 94 extends from the upper end of the
feed electrode 90 approximately halfway in the longitudinal
direction of the substrate 88, and thereafter, bends in an arch
shape so as to be quickly separated from the non-feed radiation
electrode 96. That is, the effective line length of the 94 is set
to be less than that of the feed radiation electrode 93. The open
end of the feed radiation electrode 94 is connected to a
capacitance-charging electrode 100 which is provided on the side
surface of the long-edge side facing the single antenna 81, at a
position relatively near the feed electrode 90. Fixed electrodes
101 are provided.
A common feeding terminal pattern 102 and feeding patterns 103 and
104 connected to the pattern 102 are provided in the end portion of
the circuit substrate 80 having the two single antennas 81 and 82
mounted thereon. The feed electrode 89 of the single antenna 81 is
connected to the feed pattern 103. The feed electrode 90 of the
single antenna 82 is connected to the feed pattern 104. The ground
electrodes 90 and 91 and the fixed electrodes 101 are connected to
ground patterns not shown in the drawing. The tops of the
capacitance-charging electrodes 97, 98, 99, and 100 are opposed to
ground patterns not shown in the drawing.
According to the above-described configuration, the feed element 83
and the non-feed element 85 of the single antenna 81 are
double-resonated in the same frequency band, for example, in a
frequency band of 800 to 900 MHz. The feed element 84 and the
non-feed element 86 of the single antenna 82 are double-resonated
in the same frequency band higher than that of the single antenna
81, for example, in a frequency band of 1800 to 1900 MHz.
Accordingly, the feed radiation electrodes 93 and 94 operate
similar to branched electrodes having the feeding terminal pattern
102 as a base portion thereof, similarly to the feed element 31
shown in FIG. 4.
According to the antenna device formed using the circuit substrate
80, the interval between the single antennas 81 and 82 is
increased, depending on the area of the circuit substrate 80. Thus,
the mutual interference between the single antennas 81 and 82 is
greatly reduced. The electrical volume of the antenna device
required corresponding to the uses is determined by the size of the
circuit substrate 80. The arrangement of the single antennas 81 and
82 is easily changed.
In the antenna device according to the preferred embodiment of
FIGS. 12A and 12B, band-stop circuits 105 and 106 is provided in
the middle of the feed patterns 103 and 104. In particular, the
band-stop circuit 105 is a filter circuit which interrupts a signal
in the frequency band of the single antenna 82 and transmits a
signal in to the frequency band of the single antenna 81. On the
other hand, the band-stop circuit 106 is a filter circuit which
interrupts a signal in to the frequency band of the single antenna
81 and transmits a signal in to the frequency band of the single
antenna 82.
According to this circuit-configuration, for the single antennas 81
and 82, the feed elements provided with consideration to the
excitation conditions only, and matching for the double-resonation
is easily achieved.
In the preferred embodiments of FIGS. 12A and 12B and 13, the
single antennas 81 and 82 may have the configuration of the antenna
device shown in FIGS. 4A and 4B, instead of the configurations of
FIGS. 12A, 12B, and 12C and 13, respectively. That is, the single
antennas 81 and 82 may include the non-feed radiation elements that
are arranged on both sides of the feed element, respectively. The
single antennas 81 and 82 of this antenna device constitute
dual-band antennas each having two frequency bands. That is, this
antenna device is a multi-band antenna having a total of four
frequency bands. Accordingly, when the antenna device is mounted on
radio communication equipment, the respective frequency bands are
sequentially changed for used, or can be simultaneously used.
Moreover, a single antenna 107 having the same configuration as
that of the respective single antennas 81 and 82 shown in FIG. 13
may be added. As shown in FIG. 14, the single antenna 107 is
arranged between the single antennas 81 and 82. The feed electrode
for the single antenna 107 is connected to the feeding terminal
pattern 102 via a feeding pattern 108. A filter circuit 109 is
provided in the approximate middle of the feeding pattern 108,
similarly to the single antennas 81 and 82.
The feed element and the non-feed element of the single antenna 107
are double-resonated. Thus, the antenna device has three frequency
bands. For example, when the frequency band of the single antenna
81 is 800 to 900 MHz, the frequency band of the single antennas 107
and 82 are 1800 to 1900 MHz and 2700 to 2800 MHz, respectively.
Since the non-feed elements are arranged near and along the feed
element, optimum electromagnetic field coupling between the
respective non-feed elements and the feed element is set for each
non-feed element. Double-resonance is effectively achieved in each
of the frequency bands to which the resonance frequencies of the
non-feed elements belong, respectively. Thus, the bandwidths of the
frequency bands are greatly increased as compared to an antenna of
the related art having two frequency bands as single resonance
characteristics, respectively. Accordingly, the bandwidth of the
antenna device is greatly increased, while greatly reducing the
size and height of the antenna device.
Preferably, the feed radiation electrode includes a plurality of
branched radiation electrodes. Accordingly, a plurality of
resonance frequencies in different frequency bands is provided for
one feed element. Moreover, since the branched radiation electrodes
have effective line lengths, respectively, the resonance
frequencies are individually set.
Also, preferably, the branched radiation electrodes have effective
line lengths at which the electrodes are excited at different
resonance frequencies. Therefore, the resonance frequencies are
easily set, provided that resonance frequencies of the frequency
bands do not overlap each other. The frequencies are set for the
branched radiation electrodes.
Preferably, the single feed electrode has an effective line length
at which the single feed radiation electrode is excited at the
resonance frequencies of the fundamental wave and the higher-order
harmonics. Thus, the branched radiation electrodes corresponding to
the respective resonance frequencies are unnecessary. Accordingly,
the volume of the antenna device is reduced, and the size of the
antenna device is reduced.
Preferably, the interval between the adjacent branched radiation
electrodes of the feed element increases on the open-end side.
Therefore, deterioration of the double-resonance characteristic,
which is caused by the mutual interference between the
double-resonance pairs, reduction of the frequency bandwidths and
deterioration of the antenna gain are prevented.
Preferably, the capacitance-charging electrodes are provided in the
open ends of the radiation electrodes. Accordingly, the open end
capacities of the radiation electrodes have definite values.
Thereby, the resonance frequencies of the radiation electrodes are
easily set, and outstanding matching of the double-resonance is
achieved.
Also, preferably, the at least two non-feed radiation electrodes
are arranged along the sides of the circuit substrate,
respectively. Therefore, the gains of the non-feed elements are
improved, respectively, and also, the bandwidths of the non-feed
elements are increased.
According to the present invention, the plurality of antennas is
mounted onto the circuit substrate. The volumes of the antennas is
determined by the size of the circuit substrate. Accordingly, the
size of the antenna device is optionally increased, and the design
of the antenna device, e.g., change of the antenna layout, is
easily achieved.
Preferably, signal power is supplied to the respective antennas via
the filter circuits. Therefore, the design of the feed element for
superior matching of the antennas is easily achieved.
Preferably, each antenna is configured so as to be double-resonated
in two frequency bands. Thus, a multi-band antenna is easily
achieved, and moreover, the space required for mounting the
antennas in the radio communication equipment is greatly
reduced.
The number of options for configuration of the feeding terminal is
increased, due to the terminal pin preferably provided as the
feeding terminal.
According to the radio communication equipment of the present
invention, the width of the antenna device is substantially equal
to the length of the short sides of the circuit substrate, and the
antenna device is arranged along the three sides of the circuit
substrate. Therefore, the space of the circuit substrate is
efficiently utilized, and case currents are excited in the circuit
substrate to improve the gain of the antenna device. Moreover,
since the open ends of the non-feed radiation electrodes are
separated as much as possible, the double-resonance is achieved in
wide frequency bands. Moreover, interference between the frequency
bands is greatly reduced.
In the radio communication equipment, preferably, the open end at
the top of the non-feed radiation electrode on the low frequency
side is arranged in the direction opposite to that in which the
long side of the circuit substrate elongates so as to be more
distant from the non-feed element. Therefore, the circuit substrate
is utilized as an antenna for operation at a low frequency, such
that the gain of the antenna is improved.
According to the radio communication device of the present
invention, which uses one of the antenna devices of the present
invention having wide and plural frequency bands due to the
double-resonance, radio communication in the plural frequency bands
is achieved with one antenna device. Thus, the size of the radio
communication device is further reduced.
While preferred embodiments of the invention have been described
above, it is to be understood that variations and modifications
will be apparent to those skilled in the art without departing the
scope and spirit of the invention. The scope of the invention,
therefore, is to be determined solely by the following claims.
* * * * *